For wrapping articles, for example, tins, boxes, bottles and the like, placed on or in a carrier, such as a tray, use is often made of shrink wrapping film. For this purpose the unit to be wrapped is loosely surrounded by an envelope of shrink wrapping film, whereafter this combination is passed through a shrinking tunnel, in which such a high temperature prevails that the film shrinks and will thus snugly enclose the unit being wrapped. This known wrapping method has a number of disadvantages. Thus the presence of a shrinking tunnel not only means occupying a relatively large space, but also the consumption of considerable amounts of heating energy, as most shrink wrapping films only begin to shrink at a temperature as high as 180.degree.-200.degree. C. This latter also means that this method does not permit wrapping heat-sensitive products, while further the necessary fire fighting provisions should be present. In addition, this wrapping method does not produce a product of aesthetic appearance, as the shrink film may be of non-uniform thickness and may exhibit wrinkles, folds or holes, or be fused to the carrier.
A method of the kind specified in the opening paragraph is known from British patent application 2035250. In that prior method, a tube formed of film material is shifted over four jaws which are movable relatively to each other. By moving the jaws apart, the tube if stretched, whereafter the article to be wrapped is placed in the interior of the tube. By subsequently moving the jaws towards each other, the contracting film comes into contact with the article, which after the withdrawal of the jaws is enclosed by the taut film. One disadvantage of this prior method is that it cannot be carried out continuously, as a tube must be formed, stretched and relaxed for each individual article to be wrapped, and an article being wrapped must be discharged in the same direction as it is supplied. Furthermore, the withdrawal of the jaws along the taut film, which must remain in position around the article, may cause problems, in particular cause the film surrounding the article to wrinkle.
Furthermore, U.S. Pat. No. 3,589,091 discloses a method for wrapping articles in film, in which the film is first stretched, then loosely wrapped around the articles in tubular form, and thereafter sealed, both longitudinally of the tube and transversely thereto, to produce a wrapper that encloses the articles on all sides. This method requires the use of a special type of film namely, having a memory characteristic such that when stretched, the material does not immediately contract elastically, but only slowly returns to a less stretched condition, which characteristic is used to enable the articles to be loosely wrapped and sealed, after which the film shrinks tautly on to the articles. Thus as far as processing is concerned this stretch wrapping film is comparable to a shrink wrapping film.
It is an object of the present invention to provide a method which does not have the disadvantages described above, and gives a product of aesthetic appearance.